Toxicity Tolerance in the Carcinogenesis of Environmental Cadmium

Cadmium (Cd) is an environmental toxicant of worldwide public health significance. Diet is the main non-workplace Cd exposure source other than passive and active smoking. The intestinal absorption of Cd involves transporters for essential metals, notably iron and zinc. These transporters determine the Cd body burden because only a minuscule amount of Cd can be excreted each day. The International Agency for Research on Cancer listed Cd as a human lung carcinogen, but the current evidence suggests that the effects of Cd on cancer risk extend beyond the lung. A two-year bioassay demonstrated that Cd caused neoplasms in multiple tissues of mice. Also, several non-tumorigenic human cells transformed to malignant cells when they were exposed to a sublethal dose of Cd for a prolonged time. Cd does not directly damage DNA, but it influences gene expression through interactions with essential metals and various proteins. The present review highlights the epidemiological studies that connect an enhanced risk of various neoplastic diseases to chronic exposure to environmental Cd. Special emphasis is given to the impact of body iron stores on the absorption of Cd, and its implications for breast cancer prevention in highly susceptible groups of women. Resistance to cell death and other cancer phenotypes acquired during Cd-induced cancer cell transformation, under in vitro conditions, are briefly discussed. The potential role for the ZnT1 efflux transporter in the cellular acquisition of tolerance to Cd cytotoxicity is highlighted.

Ameliorative Effects of Zn and Se Supplementation on Heavy Metal Mixture Burden via Increased Renal Metal Excretion and Restoration of Redoxo-Inflammatory Alterations

Heavy metals (HM)in the environment have provoked global attention because of its deleterious effects. This study evaluated the protection offered by Zn or Se or both against HMM-induced alterations in the kidney. Male Sprague Dawley rats were distributed into 5 groups of 7 rats each. Group I served as normal control with unrestricted access to food and water. Group II received Cd, Pb, and As (HMM) per oral daily for 60 days while groups III and IV received HMM in addition to Zn and Se respectively for 60 days. Group V received both Zn and Se in addition to HMM for 60 days. Metal accumulation in feces was assayed at days 0, 30, and 60 while accumulation in the kidney and kidney weight were measured at day 60. Kidney function tests, NO, MDA, SOD, catalase, GSH, GPx, NO, IL-6, NF-Κb, TNFα, caspase 3, and histology were assessed. There is a significant increase in urea, creatinine, and bicarbonate ions while potassium ions decreased. There was significant increase in renal function biomarkers, MDA, NO, NF-Κb, TNFα, caspase 3, and IL-6 while SOD, catalase, GSH, and GPx decrease. Administration of HMM distorted the integrity of the rat kidney, and co-treatment with Zn or Se or both offered reasonable protection suggesting that Zn or Se could be used as an antidot against the deleterious effects of these metals.

Selenium and zinc supplementation mitigates metals-(loids) mixture- mediated cardiopulmonary toxicity via attenuation of antioxidant, anti-inflammatory and antiapoptotic mechanisms in female Sprague Dawley rats

This study evaluated the cardiopulmonary protective effects of essential elements (Zn and Se) against heavy metals mixture (HMM) exposure. Twenty five female Sprague Dawley albino rats, divided in to five groups: controls were orally treated only with distilled water; next, group 2 was exposed to HMM with the following concentrations: 20 mg/kg of Pb body weight, 0.40 mg/kg of Hg, 0.56 mg/kg of Mn, and 35 mg/kg of Al. Groups 3, 4 and 5 were exposed to HMM and co-treated with zinc chloride (ZnCl2; 0.80 mg/kg), sodium selenite (Na2SeO3;1.50 mg/kg) and both zinc chloride and sodium selenite, respectively. The experiment lasted for 60 days. Afterwards animals were sacrificed, and we conduced biochemical and histopathological examination of the heart and lungs. HMM only exposed animals had an increased levels of malondialdehyde (MDA) and nitric oxide (NO), increased IL-6 and TNF-α, attenuated SOD, GPx, CAT and GSH and caspase 3 in the heart and lungs. HMM affected NF-kB and Nrf2 in the heart muscle with histomorphological alterations. Zn and Se attenuated adverse effects of HMM exposure. Essential element supplementation ameliorated heavy metal cardiopulmonary intoxication in rats.

Selenium and zinc alleviate hepatotoxicity induced by heavy metal mixture (cadmium, mercury, lead and arsenic) via attenuation of inflammo-oxidant pathways

Heavy metals (HM) are believed to be injurious to humans. Man is exposed to them on daily basis unknowingly, with no acceptable protocol to manage its deleterious effects. These metals occur as mixture of chemicals with varying concentrations in our atmosphere. There are growing calls for the use of essential metals in mitigating the injurious effects induced by heavy metals exposure to man; therefore, the aim of this study was to evaluate the protective effects of essential metals (Zinc and Selenium) in a mixture of heavy metal toxicity. In this study, except for negative controls, all other groups were treated with lead (PbCl2 , 20 mg kg-1 ); cadmium (CdCl2 , 1.61 mg kg-1 ); mercury (HgCl2 , 0.40 mg kg-1 ), and arsenic (NaAsO3, 10 mg kg-1 ) that were formed in distilled water. Pb, Cd, As, and Hg were administered as mixtures to 35, 6 weeks old rats weighing between 80 to 100 g for 60 days. Group I served as normal control without treatment, group II positive control received HM mixture, while groups III to V received HMM with Zn, Se, and Zn + Se respectively. Animal and liver weights, HM accumulation in the liver, food intake (FI), water intake (WI), liver function test, malondialdehyde (MDA), and inflammatory/transcription factor/apoptosis markers were checked. Also, antioxidant enzymes, and histological studies were carried out. Metal mixture accumulated in the liver and caused toxicities which were ameliorated by Zn and Se administration. HM caused significant decrease in FI, WI and distorted the level of liver enzymes, lipid peroxidation, inflammatory markers, antioxidants and architecture of the liver. Co administration with Zn or Se or both reversed the distortions. This study lays credence to the evolving research on the public health implications of low dose metal mixtures and the possible ameliorative properties of Zn and Se.

Selenium and zinc protect against heavy metal mixture-induced, olfactory bulb and hippocampal damage by augmenting antioxidant capacity and activation of Nrf2-Hmox-1 signaling in male rats

PURPOSE/AIM OF THE STUDY

Heavy metals and metalloids have been implicated in neurodenerative diseases. Present study has evaluated the potential protective effects of Se and Zn on heavy metals and metalloids mixture-induced (Cd, Pb, Hg and As) toxicity in the hippocampus and olfactory bulb in male rats.

MATERIALS AND METHODS

Five groups of Wistar rats were randomly divided in to: controls, toxic metals mixture (TMM) exposed rats (PbCl2, 20 mg·kg-1; CdCl2, 1.61 mg·kg-1; HgCl2, 0.40 mg·kg-1 and NaAsO3, 10 mg·kg-1)), TMM + Zn, TMM + Se and TMM-+Zn + Se groups and were orally treated for 60 days.

RESULTS

We found that in hippocampus and olfactory bulb, TMM generated increased lipid peroxidation and diminished antioxidant capacity. These adverse effects induced by TMM were alleviated by Zn and Se co-treatment; moreover, essential trace elements (Zn and Se) decreased activity of acetylcholinesterase, reduced Cd, Pb, Hg and As bioaccumulation in hippocampus and olfactory bulb and decreased levels of TNF-α in the hippocampus. TMM treated rats had lower levels of Hmox-1 (hippocampus), higher levels of Nrf2 (olfactory bulb and hippocampus) and NF-kB (olfactory bulb). TMM treated rats showed significantly highest time in locating the escape hole. Histopathological examination revealed hypertrophied granule cells in OB of TMM exposed rats.

CONCLUSION

Zn and Se supplementation can reverse quaternary mixture-induced (Cd, Pb, Hg and As) toxicity in hippocampus and OB in male albino rats.

Selenium and zinc alleviate quaternary metal mixture -induced neurotoxicity in rats by inhibiting oxidative damage and modulating the expressions of NF-kB and Nrf2/Hmox-1 pathway

Background

This study evaluated the potential protective effects of Zn and Se in the cerebellum and cerebral cortex, two fundamentally important brain regions, in albino rats that were exposed to heavy metals mixture (Al, Pb, Hg and Mn).

Methods

Animals were divided into five groups of seven animals per group with following patterns of exposure, controls group 1 were orally treated with deionized water for 60 days; group 2 was exposed to heavy metal mixture (HMM) with following concentrations (20 mg·kg^-1 of Pb body weight; 0.40 mg·kg^-1 of Hg; 0.56 mg·kg^-1 of Mn; and 35 mg·kg^-1; of Al), while groups 3,4 and 5 were exposed to HMM and orally co-treated with zinc chloride (ZnCl₂; 0.80 mg/kg), sodium selenite (Na₂SeO₃;1.50 mg/kg) and zinc chloride plus sodium selenite (ZnCl_0.2 + Na₂SeO₃) respectively.

Results

Exposure to HMM depressed cellular antioxidant apparatus, induced generation of lipid peroxidation markers (Malondialdehyde and NO), downregulated expression of transcription factors (Nrf2, and NF-kB) and upregulated Caspase 3 levels. HMM potentiated acetylcholinesterase activity and induced moderate histopathological alterations. Nevertheless, Zn, Se and in particular Zn + Se had recovering effects on all mentioned hazardous effects produced by HMM exposure in the cerebral cortex and cerebellum.

Conclusions

Selenium and zinc exert neuroprotection via Nrf2/NF-kB signaling pathways against quaternary heavy metal mixture-induced impairments in albino Sprague Dawley rats.

Ni and Al mixture amplifies cerebellar oxido-inflammatory responses, down regulates AChE and BDNF/NGF levels in motor impairment in male albino rats

BACKGROUND

Aluminum and nickel are potent neurotoxicants to which humans are constantly exposed. Previous studies have demonstrated that these two metals can affect the motor system, but their effects on the cerebellum, a central nervous system region with the highest number of neurons, have remained largely unexplored. Therefore, we conducted a study to investigate the adverse effects of Al, Ni, and Al+Ni in vivo.

METHODS

In our study, seven male Sprague Dawley rats per group were orally exposed to deionized water, 0.2 mg/kg of Ni, 1 mg/kg of Al, and 0.2 mg/kg of Ni + 1 mg/kg of Al (as a binary heavy metals mixture; HMM), respectively.

RESULTS

Ni, Al, and HMM exposed rats accumulated higher levels of Al and Ni compared to controls, and HMM treated animals had higher levels of Ca and Fe in the cerebellum (p < 0.05). Malondialdehyde (MDA) levels were significantly (p < 0.05) higher in the HMM, Ni, and Al treated groups compared to the control group that received deionized water. Superoxide dismutase (SOD), catalase (CAT), glutathione (GSH), and glutathione peroxidase (GPx) activities were significantly (p < 0.05) reduced in the HMM, Ni, and Al treated groups compared to the control group that received deionized water. Ni, Al, and HMM significantly (p < 0.05) shortened the length of time of the grip in comparison to the control. Nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF) levels were significantly decreased in the nickel, Al, and heavy metal mixture groups compared with the control group. Moreover, there was a significant decrease in the activity of acetylcholinesterase (AChE) and a increase in cyclooxygenase-2 (COX-2) activity in the Ni, Al, and HMM treated groups compared to the control group.

CONCLUSION

HMM exposed animals had significantly poorer performance in the Rotarod test (p < 0.05) than controls. Al and Ni induced impairment of cerebellar function at various levels.

Local and Systemic Hypoxia as Inductors of Increased Aluminum and Iron Brain Accumulation Promoting the Onset of Alzheimer's Disease

Human environment is highly contaminated with aluminum, and aluminum is toxic to majority of tissues, particularly to neurons. In previous decades, aluminum exposure was frequently linked with the onset of Alzheimer's disease (AD), and increased levels of Al were detected in the brains of individuals with AD. People who live in a certain area are exposed to aluminum in a similar way (they eat the same vegetable and other foodstuffs, use similar cosmetics, and buy medications from the same manufacturer), nevertheless not all of them develop Alzheimer's disease. Majority of known risk factors for AD promote atherosclerosis and consequently reduce brain blood supply. In this review, we highlighted the significance of local (carotid disease and atherosclerosis of intracranial blood vessels) and systemic hypoxia (chronic obstructive pulmonary disease and anemia) in the development of AD. Nerve tissue is very sophisticated and sensitive to hypoxia and aluminum toxicity. As a side effect of compensatory mechanisms in case of hypoxia, neurons start to uptake aluminum and iron to a greater extent. This makes perfect a background for the gradual onset and development of AD.

Nickel and aluminium mixture elicit memory impairment by activation of oxidative stress, COX-2, and diminution of AChE, BDNF and NGF levels in cerebral cortex and hippocampus of male albino rats

This study evaluated nickel and aluminium-induced neurotoxicity, as a binary metal mixture. Twenty-eight male Sprague Dawley albino rats were weight-matched and divided into four groups. Group 1 (control) received deionized water. Group 2 and 3 received Aluminium (1 mg/kg) and Nickel (0.2 mg/kg) respectively, while Group 4 received Ni and Al mixture HMM three times a week orally for 90 days. Barnes maze tests was performed. Rats were sacrificed under pentobarbital anaesthesia, cerebral cortex and hippocampus were separated, and metal levels were measured using Atomic Absorption Spectroscopy (AAS). Malondialdehyde (MDA), catalase (CAT), glutathione content (GSH), superoxide dismutase (SOD), glutathione peroxidase (GPx), Brain Derived Neurotrophic Factor (BDNF), Nerve growth factor NGF, cyclo-oxygenase COX-2 and Acetylcholinesterase (AChE) were assayed using ELISA kits. Ni/Al binary mixture exposed rats showed a shorter latency period (though not significant) of 3.21 ± 1.40 s in comparison to 3.77 ± 1.11 (Ni only) and 3.99 ± 1.16(Al only). Ni/Al mixture gp had the lowest levels of Mg in both the hippocampus and frontal cortex when compared with the individual metals. In the hippocampus Al only exposed rats significantly showed p < 0.05 higher iron and Ca levels in comparison to Ni/Al mixture. Al alone significantly showed p < 0.05 lower levels of Fe but higher Ca than the Ni/Al mixture group. Exposure to Al only showed lower levels of BDNF in comparison to Ni/Al combination, whereas Ni/Al mixture gp had lower levels of NGF in comparison to the individual metals in the hippocampus. In the frontal cortex Ni only, group showed significantly lower BDNF in comparison to Ni/Al mixture whereas the mixture showed significantly lower NGF when compared with Al only group. There were higher levels of COX-2 in the Ni/Al mixture than individual metal treated rats in both hippocampus and frontal cortex. AChE levels in the Ni/Al mixture group was higher than Ni or Al only gps in the hippocampus whereas in the frontal cortex, Ni/Al exposed rats showed significantly lower AChE levels in comparison to Al only group. Ni, Al and Ni/Al mixture exhibited memory impairment by activation of oxidative stress, COX-2, and diminution of AChE, BDNF and NGF levels in cerebral cortex and hippocampus. The BDNF-COX-2 AChE signalling pathway may be involved in the neurotoxicity of Ni and Al.

Non-Uniform Bioaccumulation of Lead and Arsenic in Two Remote Regions of the Human Heart's Left Ventricle: A Post-Mortem Study

The extent of heavy-metal-induced cardiotoxicity is proportional to the levels of metal bioaccumulation, and it was previously assumed that heavy metals accumulate uniformly in the myocardium. Therefore, the aim of this study was to investigate concentrations of metals and metalloids in two distant regions of the left ventricle (LV), the base of the LV, and apex of the LV using inductively coupled plasma mass spectrometry (ICP-MS). We also examined the potential correlation between metal levels and the thickness of the interventricular septum in twenty LV specimens (ten from the base of LV and ten from the apex of LV) from 10 individuals (mean age 75 ± 6 years). We found significantly higher concentrations of arsenic and lead in the LV apex compared to the base of the LV. We also found a positive correlation between the concentrations of arsenic in the myocardium of LV and the thickness of the interventricular septum. Our results indicate that arsenic and lead accumulate to a higher extent in the apex of the LV compared to the base of the LV. Therefore, future studies designed to measure levels of metals in heart muscle should consider non-uniform accumulation of metals in the myocardium.

The role of cadmium in the pathogenesis of myeloid leukemia in individuals with anemia, deficiencies in vitamin D, zinc, and low calcium dietary intake

Iron deficiency, vitamin D deficiency and low calcium diet are frequent health problems with severe long- term consequences. Upon absorption from the duodenum, cadmium binds to transferrin, and cells with the highest density of transferrin receptor 1 (TfR1) take up the majority of the circulating cadmium. Nowadays, it is clear that individuals with iron deficiency anemia have increased blood levels of cadmium because of higher absorption rate, mediated by divalent metal transporter 1 (DMT1). However, the transient receptor potential vanilloid receptor 6 (TRPV6), known as a calcium carrier, is able to bind and transport cadmium as well. In the case of low calcium diet or vitamin D deficiency, TRPV6 may be overexpressed in the intestine and kidney tubules and absorbs (re-uptake in the case of renal tubules) cadmium in larger quantities, resulting in an increased cadmium blood levels. We speculate that the final event in the case of low calcium dietary diet and/or vitamin D deficiency is similar to what is observed in the case of iron deficiency, that cells with the highest levels of TfR1 (for example, megakaryocyte/erythrocyte progenitors and pro-erythroblasts) take up most of the circulating cadmium, which is powerful malignancy inductor, leading to appearance of acute myeloid leukemia (AML).

Zinc and selenium attenuate quaternary heavy metal mixture-induced testicular damage via amplification of the antioxidant system, reduction in metal accumulation, inflammatory and apoptotic biomarkers

Heavy metals (HMs) such as cadmium (Cd), lead (Pb), arsenic (As), and mercury (Hg) are highly toxic elements. They are often found together in nature as a heavy metal mixture (HMM) and are known to contribute to subfertility/infertility as environmental pollutants. This study aims to evaluate the potential benefits of treating HMM-induced testicular pathophysiology with zinc (Zn) and/or selenium (Se). Six-week-old male Sprague Dawley rats were grouped into 5 (n = 7). The control group received deionized water, while the other groups were treated with PbCl2 (20 mg kg-1), CdCl2 (1.61 mg kg-1), HgCl2 (0.40 mg kg-1), and Na2AsO3 (10 mg kg-1) in deionized water for 60 days. Additionally, groups III to V received Zn, Se, and Zn/Se, respectively, for 60 days. The study evaluated testis weight, metal accumulation, sperm analysis, FSH, LH, testosterone, prolactin, oxidative stress, antioxidants, pro-inflammatory and apoptotic markers, and presented structural changes in the testis as micrographs. HMM caused a significant increase in testis weight, metal accumulation, prolactin, oxidative stress, and pro-inflammatory and apoptotic markers, while significantly decreasing semen analysis, FSH, LH, and testosterone. Histology showed decreased spermatogenesis and spermiogenesis, as evidenced by the structure of the germ cells and spermatids. However, Zn, Se, or both ameliorated and reversed some of the observed damages. This study provides further evidence for the mitigative potential of Zn, Se, or both in reversing the damage inflicted by HMM in the testis, and as a countermeasure towards improving HM-induced decrease in public health fecundity.

Graphical abstract

Exposure to tolerable concentrations of aluminum triggers systemic and local oxidative stress and global proteomic modulation in the spinal cord of rats

The tolerable aluminum (Al) intake levels for humans are constantly under review by regulatory agencies due to novel pre-clinical evidence on the neurotoxicity of prolonged Al exposure; however, little is known about the effects of Al on the spinal cord. This study aimed to investigate potential adverse effects on both spinal cord and systemic biochemical balance after prolonged exposure to a low dose of Al. Twenty adult rats were distributed in the control (distilled water) and exposed group (8.3 mg of AlCl₃/kg/day). After 60 days, both blood and spinal cord samples were collected for oxidative stress and proteomic analyses. In plasma and erythrocytes, glutathione level was not different between groups; however, exposure to AlCl₃ significantly decreased glutathione level in the spinal cord. Thiobarbituric acid reactive substances levels in the plasma and spinal cord of animals from the control group were significantly lower than those animals exposed to AlCl₃. Exposure to AlCl₃ significantly modulated the expression of proteins associated with the cell cycle, stimulus-response, cytoskeleton, nervous system regulation, protein activity, and synaptic signaling. Therefore, prolonged exposure to a low dose of Al triggered oxidative stress and proteomic changes that may affect spinal cord homeostasis.

Banana peel extract alleviate inflammation and oxidative stress via modulation of the Nrf2/Hmox-1 and NF-κB pathways in thyroid of heavy metal mixture exposed female rats

Introduction

This is an evaluation of the effects of banana peel BP extract on the heavy metals’ mixture HMM mediated oxido-inflammatory effects in the thyroid of female albino rats.

Methods

Five groups (5 female rats/group) were treated as follows for 60 days: Group 1: Deionized water only; Group 2: (Pb, Hg, Mn and Al); Group 3: 200 mg/kg BP extract + HMM; Group 4: 400 mg/kg BP extract + HMM; Group 5: 800 mg/kg BP extract + HMM. On day 60 animals were euthanized, thyroid was harvested and used for, malondialdehyde MDA, nitric oxide NO, antioxidants, tumor necrosis factor alpha (TNF – α), interleukin 6 (IL – 6), Caspase-3, Nuclear factor erythroid 2- related factor 2 (Nrf2), Nuclear factor kappa B (NfkB) and Heme Oxygynase – 1 (Hmox-1) and histopathology.

Results

There was significant bioaccumulation of Pb, Al, Hg and MN; elevated IL-6 and Tnf-α, MDA and NO, caspase-3 and Nrf2, NF-κB and Hmox-1 in the HMM only group in comparison to the control. There was significant ( p < 0.05) decrease in SOD, CAT GSH activities in HMM only exposed group in comparison to the control deionized water group, whereas BP co-treatment with HMM significantly ( p < 0.05) increased SOD, CAT GSH activities. Co-treatment with BP extract also reversed most of these effects.

Discussion and Conclusions

BP extract may ameliorate HMM -induced thyrotoxicity in female albino rats by blunting oxido-inflammatory activities.

Increased Cortical Porosity, Reduced Cortical Thickness, and Reduced Trabecular and Cortical Microhardness of the Superolateral Femoral Neck Confer the Increased Hip Fracture Risk in Individuals with Type 2 Diabetes

Individuals with diabetes mellitus type 2 (T2DM) have approximately 30% increased risk of hip fracture; however, the main cause of the elevated fracture risk in those subjects remains unclear. Moreover, micromechanical and microarchitectural properties of the superolateral femoral neck-the common fracture-initiating site-are still unknown. We collected proximal femora of 16 men (eight with T2DM and eight controls; age: 61 ± 10 years) at autopsy. After performing post-mortem bone densitometry (DXA), the superolateral neck was excised and scanned with microcomputed tomography (microCT). We also conducted Vickers microindentation testing. T2DM and control subjects did not differ in age (p = 0.605), body mass index (p = 0.114), and femoral neck bone mineral density (BMD) (p = 0.841). Cortical porosity (Ct.Po) was higher and cortical thickness (Ct.Th) was lower in T2DM (p = 0.044, p = 0.007, respectively). Of trabecular microarchitectural parameters, only structure model index (p = 0.022) was significantly different between T2DM subjects and controls. Control group showed higher cortical (p = 0.002) and trabecular bone microhardness (p = 0.005). Increased Ct.Po and decreased Ct.Th in T2DM subjects increase the propensity to femoral neck fracture. Apart from the deteriorated cortical microarchitecture, decreased cortical and trabecular microhardness suggests altered bone composition of the superolateral femoral neck cortex and trabeculae in T2DM. Significantly deteriorated cortical microarchitecture of the superolateral femoral neck is not recognized by standard DXA measurement of the femoral neck.

Global Proteomic Profile of Aluminum-Induced Hippocampal Impairments in Rats: Are Low Doses of Aluminum Really Safe?

Hippocampus is the brain area where aluminum (Al) accumulates in abundance and is widely associated with learning and memory. In the present study, we evaluate behavioral, tissue, and proteomic changes in the hippocampus of Wistar rats caused by exposure to doses that mimic human consumption of aluminum chloride (AlCl₃) in urban areas. For this, male Wistar rats were divided into two groups: Control (distilled water) and AlCl₃ (8.3 mg/kg/day), both groups were exposed orally for 60 days. After the Al exposure protocol, cognitive functions were assessed by the Water maze test, followed by a collection for analysis of the global proteomic profile of the hippocampus by mass spectrometry. Aside from proteomic analysis, we performed a histological analysis of the hippocampus, to the determination of cell body density by cresyl violet staining in Cornu Ammonis fields (CA) 1 and 3, and hilus regions. Our results indicated that exposure to low doses of aluminum chloride triggered a decreased cognitive performance in learning and memory, being associated with the deregulation of proteins expression, mainly those related to the regulation of the cytoskeleton, cellular metabolism, mitochondrial activity, redox regulation, nervous system regulation, and synaptic signaling, reduced cell body density in CA1, CA3, and hilus.

Global Scientific Research Landscape on Aluminum Toxicology

This study aimed to identify the landscape of current aluminum toxicity based on knowledge mapping of the 100 most-cited articles on toxicological aspects of aluminum in biological organisms. The research was searched in the Web of Science Core Collection (WoS-CC) with publications between 1945 and 2022. Data regarding authorship, title, journal, year of publication, citation count, country, keywords, study design, and research hotspots were extracted and all elected articles were analyzed. Our results showed that among the articles selected, literature review and in vivo studies were the most common study designs. The USA and England were found as the countries with most publications. Alzheimer's disease (AD), aluminum, and neurotoxicity were found as the most frequent keywords. The articles most cited in world literature suggested that aluminum exposure is associated with Alzheimer's disease, Parkinson's disease (PD), dialysis encephalopathy, amyotrophic lateral sclerosis, neurodegeneration changes, cognitive impairment, such as bone damage, oxidative alterations, and cytotoxicity.

Three-dimensional mapping of cortical porosity and thickness along the superolateral femoral neck in older women

Although several studies have analyzed inter-individual differences in the femoral neck cortical microstructure, intra-individual variations have not been comprehensively evaluated. By using microCT, we mapped cortical pore volume fraction (Ct.Po) and thickness (Ct.Th) along the superolateral femoral neck in 14 older women (age: 77.1 ± 9.8 years) to identify subregions and segments with high porosity and/or low thickness—potential “critical” spots where a fracture could start. We showed that Ct.Po and Ct.Th significantly differed between basicervical, midcervical, and subcapital subregions of the femoral neck (p < 0.001), where the subcapital subregion showed the lowest mean Ct.Th and the highest mean Ct.Po. These cortical parameters also varied substantially with age and with the location of the analyzed microsegments along the individual’s neck (p < 0.001), showing multiple microsegments with high porosity and/or low thickness. Although the highest ratio of these microsegments was found in the subcapital subregion, they were also present at other examined subregions, which may provide an anatomical basis for explaining the fracture initiation at various sites of the superolateral neck. Given that fractures likely start at structurally and mechanically weaker spots, intra-individual variability in Ct.Po and Ct.Th should be considered and the average values for the entire femoral neck should be interpreted with caution.

Aluminum bone toxicity in infants may be promoted by iron deficiency

Aluminum has adverse effects on human health. Aluminum is poorly transported from the gastrointestinal tract, but if the load is high, a significant level of aluminum may be absorbed. There are two main sources of aluminum in infants - adapted formulas (when an infant is predominantly fed with it), and vaccines. After aluminum enters the circulation, it binds to transferrin and remains mainly in the skeleton for a longer period of time. Transferrin receptor 1 (TfR1) is highly expressed on osteoblast-like cells whereas the number of TfR1 may additionally rise in case of iron deficiency. Since iron deficiency can induce the additional expression of TfR1, a larger quantities of aluminum may be uptaken by osteoblasts and consequently aluminum may decrease the number of osteoblasts and lead peak bone mass (PBM) closer to the osteoporotic threshold. Iron deficiency may potentiate aluminum-induced toxicity to bones. Aluminum burden in infants has always been considered as harmless whereas a potential increased toxicity of aluminum in high-sensitive infants caused by iron deficiency has not been evaluated.

Vascular Complications in Individuals with Type 2 Diabetes Mellitus Additionally Increase the Risk of Femoral Neck Fractures Due to Deteriorated Trabecular Microarchitecture

Individuals with diabetes mellitus type 2 (T2DM) have an increased risk of hip fracture, especially if vascular complications are present. However, microstructural origins of increased bone fragility in T2DM are still controversial. DXA measurement of the contralateral hip and three-dimensional microCT analyses of femoral neck trabecular microarchitecture were performed in 32 individuals (26 women and 6 men, 78 ± 7 years). The specimens were divided to two groups: T2DM individuals with hip fracture (DMFx, n = 18) and healthy controls (CTL, n = 14). DMFx group consisted of individuals with vascular complications (DMFx_VD, n = 8) and those without vascular complications (DMFx_NVD, n = 10). T-score was significantly lower in DMFx_VD and DMFx_NVD than in controls (p < 0.001). BV/TV, Tb.N, Tb.Sp, SMI, and FD varied among DMFx_NVD, DMFx_VD, and CTL groups (p = 0.023, p = 0.004, p = 0.008, p = 0.001, p = 0.007, respectively). Specifically, BV/TV of DMFx_VD was significantly lower than that of DMFx_NVD group (p = 0.020); DMFx_NVD group had higher Tb.N and lower Tb.Sp compared with DMFx_VD (p = 0.006, p = 0.012, respectively) and CTL (p = 0.026, p = 0.035, respectively). DMFx group and healthy controls showed similar BV/TV, Tb.Th, Tb.N, Tb.Sp, Conn.D, DA, and FD (p = 0.771, p = 0.503, p = 0.285, p = 0.266, p = 0.208, p = 0.235, p = 0.688, respectively), while SMI was significantly higher in controls (p = 0.005). Two distinct phenotypes of bone fragility were identified in T2DM patients: patients with vascular complications showed impaired trabecular microarchitecture, whereas bone fragility in the group without vascular complications was independent on trabecular microarchitecture pattern. Such heterogeneity among T2DM patients may explain contradicting literature data and may set a basis for further studies to evaluate fracture risk related to T2DM.

Three-Dimensional Microstructural Basis for Differential Occurrence of Subcapital versus Basicervical Hip Fractures in Men

We analyzed the bone microarchitecture of the subcapital and basicervical subregions of the femoral neck in men, to determine whether microarchitectural differences of cortical or trabecular bone can explain differential frequency of subcapital vs. basicervical fractures, especially in aged persons. The study sample encompassed twenty male proximal femora obtained during autopsy. They were divided in two age groups: young (< 40 years, n = 10) and aged (> 60 years, n = 10). Micro-computed tomography was used to evaluate cortical and trabecular microarchitecture of the subcapital and basicervical regions of the superolateral femoral neck-typical fracture initiation site. Basicervical region showed significantly thicker and less porous cortex than subcapital region (p = 0.02, p < 0.001, respectively), along with increased distance between cortical pores (p = 0.004) and smaller pore diameters (p = 0.069). Higher trabecular number (Tb.N: p = 0.042), lower trabecular thickness (Tb.Th: p < 0.001), and lower trabecular separation (p = 0.003) were also hallmarks of the basicervical compared to subcapital region, although BV/TV was similar in both regions (p = 0.133). Age-related deterioration was mostly visible in trabecular bone (for BV/TV, Tb.Th, Tb.N and fractal dimension: p = 0.026, p = 0.049, p = 0.059, p = 0.009, respectively). Moreover, there were tendencies to age-specific patterns of trabecular separation (more pronounced inter-site differences in aged) and cortical thickness (more pronounced inter-site differences in young). Trabecular microarchitecture corresponded to cortical characteristics of each region. Our study revealed the microarchitectural basis for higher incidence of subcapital than basicervical fractures of the femoral neck. This is essential for better understanding of the fracture risk, as well as for future strategies to prevent hip fractures and their complications.

"Dangerous duo": Chronic nicotine exposure intensifies diabetes mellitus-related deterioration in bone microstructure - An experimental study in rats

AIMS

Bony complications of diabetes mellitus (DM) are still insufficiently understood. Our aims were to analyze the individual and combined effects of chronic hyperglycemia and nicotine exposure on the femoral trabecular and cortical microarchitecture on a rat experimental model.

MAIN METHODS

The micro-computed tomography based bone microstructural evaluation was performed on male Wistar rats divided into four groups: control (n = 7), experimentally-induced DM (n = 8), chronically exposed to nicotine (n = 9) and the DM group exposed chronically to nicotine (n = 9).

KEY FINDINGS

Chronic hyperglycemia caused mild trabecular deterioration; yet, the combination of hyperglycemia and nicotine exposure showed more deleterious effects on the trabecular bone. Namely, the DM + nicotine group had significantly lower bone volume fraction, fewer and more rod-like shaped trabeculae, along with higher trabecular separation and lower connectivity than the control group (p < 0.05). Nicotine alone did not show any significant deterioration compared to the control group. DM and DM + nicotine groups had lower cortical porosity than control and nicotine groups (p < 0.05). Cortical thickness did not show any significant intergroup differences, whereas bone perimeter and the mean polar moment of inertia were reduced in DM + nicotine group.

SIGNIFICANCE

Mild effects of chronic hyperglycemia on bone structure were accentuated by the chronic nicotine exposure, although nicotine alone did not cause any significant bone changes. That suggests a synergistic effect of hyperglycemia and nicotine on bone deterioration and increased propensity to fracture. Indeed, better understanding of risk factors driving bone structural deterioration is a precondition to limit the complications associated with DM.